After a few searches it appears this is comparable to Ace Hardware's house brand of black silicone and Complies with MIL-A-46106A and FDA 177.2600. Not sure what the MIL-A number is but the FDA number I believe is "food safe".

I would avoid the GE 2. It's not just roots that you should be worried about. It's the fact that the organotins used in the curing process are known to have negative effects in animals.

The other two products, I am not familiar with; however, you said they are "old stock." This alone would make me steer clear. Older silicone will sometimes not cure and it's just not worth it for something that is so cheap and easy to replace. Also, you linked the product data sheets but what you really want to know comes from the MSDS, not the product data sheet. I am not enough of a chemist to know how to read these but maybe someone else can chime in.

As for what is safe to use, there are some known options. If you just need clear, my big box stores still sell GE 1 (which is safe because it doesn't use an organotin catalyst). You can also buy ASI Aquarium Sealant for cheap online and it comes in clear or black. I have had great luck with CR Lawrence black silicone, too, and it is relatively inexpensive. I use clear anywhere it won't be seen and black for anywhere it will :-)

Older silicone will sometimes not cure and it's just not worth it for something that is so cheap and easy to replace.

Gospel Truth here. Don't mess around with old silicone. You can have a horrible, horrible mess to clean up. When it just sits there and remains sticky and stinky - man, that sucks. It's one thing if you're just trying to join glass to glass and can pull the panes apart, wipe down, and start over. But if you put it inside a partly-built viv, got it on your cork or driftwood etc? Horrible.

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As for what is safe to use, there are some known options. If you just need clear, my big box stores still sell GE 1 (which is safe because it doesn't use an organotin catalyst). You can also buy ASI Aquarium Sealant for cheap online and it comes in clear or black. I have had great luck with CR Lawrence black silicone, too, and it is relatively inexpensive. I use clear anywhere it won't be seen and black for anywhere it will :-)

I can also speak for the clear GE1 and the black ASI. My personal "rule" for color is the same - clear behind the scenes, and black anywhere I might have to look at the crap. I really, really, really don't like looking at silicone in my builds.

So I opened the Dow Corning tube because "why not" and I figured I could leave some out and see if it would cure or not. All four tubes were solid. Just because I could, I cut the tube off of the silicone and now have a solid tube of black silicone without the tube.

Returning the GE 2 and getting a tube of clear GE 1 and being done with it.

Thanks for letting me know what the worst case scenario would be with old silicone.